This chart shows you the range of platter-to-buffer transfer rates from the innermost track to the outermost track. In other words, it shows you the range of disk transfer rates of the hard drives (from minimum and maximum).

The platter profile of the 4 TB Western Digital Blue SSHD we received was very good. There were no noticeable dips in throughput that would signify a significant use of replacement sectors. Lots of them would point to poor platter quality.

We also compared its platter profile to that of the 4 TB Western Digital Red (WD40EFRX), which uses the same 1 TB platters. You can see the Red drive is slightly slower across the platter. This points to a slightly slower spindle speed - probably just 5200 RPM.